Oil compositions containing soapsalt mixtures



United States Patent Ofiiice 3,077,450 Patented Feb. 12, 1063 This invention relates to oil compositions containing alkaline earth metal salts of acetic acid and alkaline earth metal soap of C to C mono-unsatura-ted fatty acid, and methods for their preparation. Particularly, the invention relates to oil compositions containing alkaline earth metal salt of acetic acid and alkaline earth metal soap of C to C unsaturated fatty acids obtained from either vegetable or animal sources, wherein the molar proportion of salt to soap is on the order of 100:1 to 1,000: 1.

Recently, lubricating oil compositions containing alkaline earth metal salts of acetic acid in combination with alkaline earth metal soap of higher molecular weight saturated fatty acids have found widespread use in commercial applications. These soap-salt lubricants (particularly when made from calcium) have good anti-wear and loadcarrying ability, which properties have made them cornmercially successful. Solid grease compositions, fluid and semi-fluid lubricants have been prepared containing these soap-salt materials. One type of such lubricant has been described in .U.S. Patent 2,846,392. This patenttaught that by drastically increasing the amount of salt, e.g. acetate, relative to the soap of higher molecular Weight fatty acid, to as much as 40 molar equivalent proportions or more, the load-carrying and other beneficial properties of the lubricant could be improved. It has now been found that if the soap is prepared from a mono-unsaturated fatty acid that it is possible to form stable oil dispersions ofsaltsoap combinations in molar ratios in excess of 100 and as high as 1,000 moles of salt of acetic acid per mole of soap of higher fatty acid. It has been further found that in preparing such soap-salt lubricants, the use of mono-unsaturated fatty acids in the preparation results in a softer grease as compared to the grease formed by using a like amountof a saturated fatty acid. Because of this lesser thickening effect of the unsaturated acids, a relatively larger amount of metal can be included inthe lubricant. This, in turn, results in lubricants having higher load-carrying ability than can be obtained byusing the more conventional saturated fatty acid soap.

It has been further found that the use of the unsaturated acid in preparing soap-salt grease reduces hard crust formation and excessive hardening which occurs during a relatively short storage time when the grease is prepared from saturated fatty acids or glycerides of fatty acids.

In brief, the present invention relates to soap-salt oil compositions, particularly lubricating greases, prepared from unsaturated fatty acids and acetic acid or anhydride, which greases have higher load-carrying ability, do not form crust or harden excessively upon storage. In addition, by use of these relative high molar ratios, concentrates can be formed which in turn can be blended in with other preformed soap greases. The resulting mixed grease is found to have many of the properties of the prior art soap-salt greases, and at the same time represents a more simple manufacturing step in avoiding heating large amounts of material at high temperatures. Fluid lubricants and semi-fluid lubricants can also be prepared in these high mole ratios.

The soap-salt concentrates of the invention are usually prepared by coneutralizing the acids, in situ in oil, with alkaline earth metal base.

The acetic acid portion of the thickener'is preferably obtained by use of acetic anhydride rather than acetic acid,

particularly when calcium hydroxide is used as a metal base. Although both are operable, it has been found that the acetic acid does not react as rapidly with the calcium hydroxide as does acetic anhydride and longer heating periods are required to remove the water of reaction.

The unsaturated acids used to prepare the lubricants include C to C preferably C to C mono-unsaturated straight chain fatty acids. Such fatty acids will include tallo-w fatty acids, oleic, palrnitoleic, gadoleic, erucic,

.arachidonic, myristoleic acid, etc. These fatty acids may be derived from either animal or vegetable sources. In some cases the commercial acids derived from naturally occurring materials may contain up to about 40 or even 50-wt. percent of saturated fatty acids along with very minor amounts (e.g. 2 to 5%) of polyunsaturated fatty acids. However, these mixed materials are operable in the present invention provided they have iodine numbers of about 35 to 110, preferably 45 to 95,;and saponitication numbers of 250 to 150, preferably 225 to 175 mg. KOH/ gm.

The alkaline earth metal component of the soap-salt composition of the invention include calcium, barium, strontium and magnesium, although calcium is preferred. Usually, the acids are neutralized with alkaline earth metal base, egg. 2. hydroxide, oxide or carbonate. Lime (calcium hydroxide) is preferred.

The compositions of the invention are readily prepared by co-neutralizing the acetic acid or anhydride and the mono-unsaturated fatty acid material with alkaline earth metal base, followed by dehydration and heating to temperatures of 225 to 550 F., preferably 270 .to 350 F.

Alternatively, no external'heating may be applied with the result that the water of reaction is left in the lubricant. In cases where the lubricant is designed for low temperature use, this is not objectionable. The acetic acid or anhydride and the unsaturated acid can be used in hydrogen equivalent molar ratios of as low as 2:1 to as high as 1000: 1. However, in the preferred form of theinvention, compositions are prepared utilizing to 1000, e.g. 200 to 600, mol'hydrogen equivalents of acetic acid or anhydride per mol hydrogen equivalent of unsaturated acid. These compositions are then used to modify other preformed greases. Preformed soap and salt can be simply mixed in oil and heated if desired, but is less preferred to the in situ preparation outlined above.

The compositions of the invention will comprise lubrieating oil and 3 to 60 wt. percent preferably 10 to 50 Wt. percent, based on the weight of total composition, of the soap-salt.

The oil component of the composition can be a mineral lubricating oil or a synthetic lubricating oil. Such synthetic oils will include diesters such as di-Z-ethylhexyl sebacate, complex esters, carbonate esters, polysilicones and other synthetic oils.

Thecompositions of the invention can also include conventional additives in amounts of 0.05 to 10.0 wt. percent, based on total composition. For example, oxidation in hibitors such as phenyl-alpha-naphthylamine; rust inhibitors such as sodium nitrite and lanolin; dyes, etc. can be used. Minor amounts (e.g. 0.1 to 10.0) wt. percent of other acids may also be present when the co-neutralization is carried out as outlined above, cg. sulfuric acid, nitric acid, phosphoric acid, etc.

The compositions of the invention may also be mixed with any other type lubricant compositions in any propertions. Thus, by the addition of 0.1 to 1.0 part by weight of the lubricant of the invention per 1 part by weight of simple soap grease, the anti-wear and extreme pressure properties of the simple soap grease are improved. The same is true of other grease systems. Greases which may be improved in this way will include lubricating oils thickened with salts, soaps, other soap-salt or mixedsalt systems, polymeric thickeners (e.g. polymers of C to C monoolefins of 10,000 to 200,000 molecular weight such as polyethylene), and inorganic thickeners (e.g. clay, carbon black, silica gel, etc.). Generally, these other greases will comprise either a synthetic or mineral lubricating oil thickened with about 3 to 50 wt. percent, usually to 40 wt. percent, of a thickener. In the case of other soap-salt and mixed-salt thickeners, the thickener is usually formed by co-neutralization in oil, by metal base, of various mixtures of high molecular weight saturated fatty acids and/or intermediate molecular weight fatty acids with low molecular weight fatty acids.

The invention will be further understood by reference to the following examples, wherein all parts are by weight.

GREASE A 22.40 parts of hydrated lime, 0.35 part of animal fatty acid and 46.25 parts of a mineral lubricating oil having a viscosity of 55 SUS at 210 F. were added to a steam-heated grease kettle and intimately mixed. 30.0 parts of acetic anhydride was then slowly added and the temperature of the mixture rose to 200 F. Next, external heating was initiated and the composition heated to about 320 F. until dehydrated, then cooled to 200 F. where 1 part of phenyl-alpha-naphthylamine was added as an oxidation inhibitor. Then the composition was cooled to 100 F. The grease was then homogenized by passing through a Morehouse mill having an 0.003" clearance. The animal fatty acid used was tallow fatty acid having an iodine number of 47.5 and a saponiiication number of 206 mg. KOH/gm. of acid.

GREASE B A simple soap grease was prepared by heating a mixture of 12 parts of animal fat, 1.75 parts hydrated lime and 85.5 parts mineral oil to a temperature of 300 F. until the soap formed and the material began to thicken. The mixture was then cooled to 200 P. where .75 part of water was added in order to give the composition a fibrous appearance and to hold the soap particles together. The material was then cooled to 175 F., where it was filtered through a Purolator 60 mesh filter and d grease A and 60 parts of grease B by simple mixing at 100 F. To the resulting mixed grease, 1.2 parts of 35 micron sodium nitrite was added dispersed in 1.2 parts of mineral lubricating oil. The sodium nitrite was added solely as a rust inhibitor.

GREASE D A grease was prepared as follows: 18.5 parts of hydrated lime, 0.73 part of Emery 3286-5 acid and 254.77 parts of mineral lubricating oil having a viscosity of 55 SUS at 210 F. were mixed together. Then 25 parts of acetic anhydride was slowly added. The resulting mixture was dehydrated at 320 F., cooled to 200 F. where 1 part of phenyl-alpha-naphthylamine was added, then cooled to 100 F. and homogenized in a Morehouse mill having an 0.003" clearance. The Emery 3286-8 acid is a low cost mono-unsaturated vegetable fatty acid having an iodine number of 94 and a saponification number of 189 mg. KOH/gm. and comprising primarily isooleic acid.

GREASE E parts of grease D was blended with 50 parts of mineral lubriacting oil of SUS at 210 F.

GREASE F For comparison purposes, an attempt was made to prepare a grease similar to that of grease A by the same procedure, but using saturated fatty acid, namely Hydrofol Acid 51 in place of the unsaturated acid. The Hydrofol Acid 51 is a commercial acid formed by bydrogenating fish oil acid and is similar to stearic acid in degree of saturation and average carbon chain length. However, the resulting soap-salt thickener system became so hard, that when only one-half the amount of acetic anhydride had been added, the kettle paddle could not be turned.

GREASE G A comparison grease was prepared employing acetic anhydride and saturated fatty acids consisting of equal portions of l2-hydroxy stearic acid and Hydrofol Acids 51 in a molar proportion of 10:1.

The compositions of the preceding greases and their properties are summarized in the following table:

Table I Composition (Parts by weight) Grease Acetic Anliydride Animal Fatty AcltL.-. Animal Fat O Hydrated Lime Phenyl u-Naphthylamine Mineral Lubricating Oil (55 SUS at 210 F.) Water Moi Equivalent Ratio of Acetic Anhydridc to Higher Fatty Acid Properties:

Dropping Point, "F

Penetrations, 77 F., mm./l0

Unworked Worked Strokes. Worked 10,000 Strokes Lubrication Life in ms. 250 F.-10,000

r.p.m.) Tirnren flgst, Lbs.-

arrie 50 r.

Failed 1 ABEO-NLGI Spindle Test.

packaged. The animal fat was fieshing fat having an iodine number of 45.4 and a saponification number of 199 mg. KOH/gm.

GREASE C As seen by the above table, the unsaturated fatty acids can form soap-salt greases prepared from very high molar ratios of acetic anhydride to unsaturated acids as shown by grease A. Grease B shows a simple soap-grease pre- A mixed grease was formed consisting of 40 parts of pared from animal fat having a low dropping point and a low lubrication life. Upon the blending of greases A and B to form grease C, the resulting composition had a dropping point in excess of 500 F. and a lubrication life in excess of 2,000 hours. This, therefore, illustrates the fact that not only may very high ratios of salt to soap of unsaturated acid be used, but the resulting compositions can be used to improve the properties of simple preformed grease mixtures. Grease D illustrates a high molar ratio material prepared from a vegetable fatty acid, namely Emery 3286-8 acid. Grease E illustrates how grease D can be diluted to form a fluid lubricant having extremely high extreme pressure properties as measured in the Tim'ken test. The first comparison grease, grease F, having a high soap-salt content could not be prepared at all when using a saturated fatty acid with a salt to soap ratio of 500 to 1. Grease G illustrates the lower extreme pressure properties that result when the thickener content and mol ratio are reduced. Furthermore, grease G was not very stable to working. And while it carried a 33 pound load in the Timken test, it was borderline to a failure at this load. At 40 pound load, it was a complete failure, resulting in a broad abrasive scar. While not shown in the table, grease G hardened after 6 months storage to a 60 stroke worked penetration of 175 mrn./10, while the greases of the invention did not appreciably harden.

To further illustrate the invention a grease may be prepared exactly in accordance with the preparation of grease A, previously described by using .35 part of oleic acid in place of the animal fatty acid of grease A.

What is claimed is:

l. A lubricant composition consisting essentially of a lubricating oil and about 3 to 60 wt. percent, based on the weight of the total composition, of a soap-salt mixture consisting essentially of alkaline earth metal salt of acetic acid and alkaline earth metal soap of G to C fatty acid having an iodine number within the range of 35 to 110, and a saponification number within the 6 range of 250 to 150 mg. KOH/gm, wherein a major proportion of said C to C fatty acid is mono-unsaturated, wherein the 11101 equivalent ratio of said salt to said soap is within the range of about 100:1 to 1,000z1 and wherein said salt and said soap are the sole metal salts of fatty acid present in said composition.

2. A lubricant composition according to claim 1, wherein said alkaline earth metal is calcium.

3. A lubricant composition according to claim 1, wherein said fatty acid is C to C acid.

4. A lubricant composition according to claim 1, wherein said acetic acid is supplied by acetic anhydride.

5. A method of preparing a lubricating grease which comprises co-neutralizing in lubricating oil with alkaline earth metal base, acetic anhydride and C to C fatty acid as the sole fatty acid, followed by heating to temperatures of 225 to 550 F. to dehydrate the grease of its water of reaction and then cooling, wherein the mol equivalent ratio of said acetic anhydride to said fatty acid is within the range of 100:1 to 1,000z1, wherein said fatty acid has an iodine number within the range of to and a saponification number within the range of 225 to mg. KOH/gm., and wherein said fatty acid includes a major proportion of mono-unsaturated fatty acid.

6. A lubricant composition according to claim 1, which also contains about 1.0 wt. percent of phenyl-alpha-naphthylamine as an oxidation inhibitor.

7. A lubricant composition according to claim 1, wherein said oil is a mineral lubricating oil, the amount of said soap-salt is about 10 to 50 wt. percent, and said molar ratio is about 200:1 to 600:1.

References Cited in the file of this patent UNITED STATES PATENTS 2,844,536 Morway July 22, 1958 2,846,392 Morway et al. Aug. 5, 1958 2,909,485 Beerbower et al. Oct. 20, 1959 

1. A LUBRICANT COMPOSITION CONSISTING ESSENTIALLY OF A LUBRICATING OIL AND ABOUT 3 TO 60 WT. PERCENT, BASED ON THE WEIGHT OF THE TOTAL COMPOSITION, OF A SOAP-SALT MIXTURE CONSISTING ESSENTIALLY OF ALKALINE EARTH METAL SALT OF ACETIC ACID AND ALKALINE EARTH METAL SOAP OF C14 TO C30 FATTY ACID HAVING AN IODINE NUMBER WITHIN THE RANGE OF 35 TO 110, AND A SAPONIFICATION NUMBER WITHIN THE RANGE OF 250 TO 150 MG. KOH/GM., WHEREIN A MAJOR PROPORTION OF SAID C14 TO C30 FATTY ACIDS IS MONO-UNSATURATED WHEREIN THE MOL EQUIVALENT RATIO OF SAID SALT TO SAID SOAP IS WITHIN THE RANGE OF ABOUT 100:1 TO 1,000:1 AND WHEREIN SAID SALT AND SAID SOAP ARE THE SOLE METAL SALTS OF FATTY ACID PRESENT IN SAID COMPOSITION. 